The dust generated in the electric arc furnace (herein after EAF) is extremely fine and is formed by metal vaporization, subsequent reaction with the oxygen within the furnace, and deposition on condensed nuclei. Such a dust formation process is a result of the high temperatures generated in the arc zone, the oxygen jet-melt interactions, melt boiling during refining and because tramp metals, such as zinc, lead and cadmium, are highly volatile at the temperatures of the molten steel. This EAF dust is a hazardous waste due to the leachability of the toxic tramp elements of lead, cadmium and chromium.
Due to the undesirable elements of sodium, potassium, zinc and lead, recycle of flue dust in the steel plant is not prudent. In addition, the dust is extemely fine and difficult to handle and transport.
The dust is presently being disposed of in landfills onsite or at a licensed outside facility.
The dust with 15-25% Zn is presently being disposed of in landfills on-site or at a licensed outside facility, the dust of high zinc content, &gt;25% is sufficiently rich in zinc to be processed by zinc refiners or by fertilizer manufacturers.
Besides the zinc recovery, the trend is to develop processes or practices for recovery of the iron and slag from low-level zinc dust in order to get a more economic process.
Two of the processes offering the best prospects for success are the plasma driven direct reduction process and a process involving solvent extraction chemistry to produce a high quality zinc metal powder.
However, both plasma and solvent extraction processes require too much capital and operating cost, and are too technically sophisticated.